1. Field of the Invention
The present invention relates to a pin plug which is a connecting apparatus to be connected to a jack, etc., for connecting electric components to each other.
2. Description of the Related Art
There were pin plugs of this kind such as disclosed in the following literatures;
Literature 1: Japanese Utility Model Publication No. 63-25668
Literature 2: Electronic Industries Association of Japan Specification "RC-6703A pin connector for electronic components" (1988-7) published by Electronic Industries Association of Japan (Inc.) Technical Department.
FIG. 1 is a longitudinal cross-sectional view of a conventional pin plug described in the literature 1 set forth above and FIG. 2 is an enlarged cross-sectional view thereof cut along II--II line.
The pin plug 10 is inserted into or extracted from, for example, a jack 20. The jack 20 comprises a cylindrical metal sleeve 21 and a female electric contact 22 which is fixed in the metal sleeve 21 by way of an insulator.
The pin plug 10 comprises a cylindrical metal sleeve 11 which is inserted outside the sleeve 21 of the jack 20, a metal center pin 12 which is arranged along the axis of the sleeve 11 and contacts the female electric contact 22 of the jack 20, an insulator 13 which electrically insulates the sleeve 11 from the center pin 12 and fix them to each other and a synthetic resin cover 14 which engages the outside of the sleeve 11.
The sleeve 11 includes a cylindrical head portion 11a and a cord clamping portion 11b extended therefrom, both of which are, for example, made of a sheet of metal plate. The cylindrical head portion 11a is formed of a sheet of metal plate machined into a cylindrical shape having a slit 11c therein. The cord clamping portion 11b of the sleeve 11 fixedly clamps a cord 30, and the second conductor of the cord 30 (e.g., a cable sheath) 32 is fixed to the cord clamping portion 11b by spot welding etc. A center pin 12 is arranged along the axis of the cylindrical head portion 11a. The center pin 12 is connected to a first conductor of the cord 30 (e.g., a cable core) 31 at the rear half portion thereof by spot welding etc., and the rear half portion of the center pin 12 and the sleeve 11 are fixed to each other by a resin insulator 13 so as to form a cylindrical form having the same diameter as that of the head portion 11a. A cover 14 engages the outside of the insulator 13 and the sleeve 11.
The assembling of the pin plug of this kind and the connection thereof to the cord 30 are performed as follows.
The center pin 12 is inserted into the head portion 11a of the sleeve 11 along the axis thereof and the cylindrical insulator 13 having the same diameter as that of the head portion 11a and fixing the rear half of the center pin 12 therein is formed between the head portion 11a and the cord clamping portion 11b by way of resin insert. Then the cord 30 piercing the cover 14 is clamped by the cord clamping portion 11b of the sleeve 11, the cable sheath 32 of the cord 30 is connected to the cord clamping portion 11b by spot welding etc., and the cable conductor 31 of the cord 30 is connected to the center pin 12 at the rear side surface thereof by spot welding etc.
Thereafter the cover 14 is forced to be put on the sleeve 11 from the rear side thereof toward the head portion 11a so as to cover the same. In this way the assembling of the pin plug and the connection of the cord 30 thereto are completed.
When the tip end of the center pin 12 of the thus assembled pin plug 10 is inserted into the female contact 22 of the jack 20, the sleeve 11 of the pin plug 10 engages the outside of the sleeve 21 of the jack 20, so that the center pin 12 of the pin plug 10 is electrically coupled to the female contact 22 of the jack 20 and the sleeve 11 of the pin plug 10 is electrically coupled to the sleeve 21 of the jack 20.
The conventional pin plug, however, had the following drawbacks.
In the conventional pin plug 10, the sleeve 11 is made of, for example, a sheet of metal plate by press molding, etc. for manufacturing simplification, cost reduction, etc. and has a cylindrically formed head portion 11a. Since the cylindrical head portion 11a is made of a sheet of metal plate, it has a slit 11c, which makes the head portion 11a displaceable and elastic in the radial direction thereof. The elasticity of the head portion 11a of the sleeve 11, however, is poor due to its construction.
The diameter of the head portion 11a of the sleeve 11 is determined by a technical standard as described in the literature 2, etc., set forth above, with a strict allowable error of, e.g., .PHI. 8.3.+-.0.1 (mm). As a result, when the diameter of the head portion 11a of the sleeve 11 is too large due to a manufacturing variation, there occurs a defective electrical contact between the sleeve 21 of the jack 20 and itself. On the contrary, when it is too small, it can hardly be inserted into or extracted from the sleeve 21 of the jack 20. At that time, if the head portion 11a having a small diameter is forced to be set outside the sleeve 21 of the jack 20, there is a likelihood of defective electric contact between the sleeve 21 and itself since the sleeve 21 enlarges the slit 11c so that the head portion 11a is deformed to be elliptical in cross section and the contacting area between the head portion 11a and the sleeve 21 is lessened.
Moreover, there were drawbacks such as the poor corrosion resistance of the metal head portion 11a of the sleeve 11, and furthermore, the difficulty of coloring for color code identification of pin plugs.
It is the first object of the present invention to provide a pin plug which comprises a sleeve and an insulator integrally formed with a rigid resin and has a two-partitioned structure, so as to increase accuracy in the diameter of the cylindrical sleeve portion at manufacturing and be easily assembled without any specific tool.
It is the second object of the present invention to provide a pin plug comprising a flexible metal contact piece at the opening formed at a portion of the circumference of the cylindrical sleeve thereof and a non-rigid resin cover which presses the contact piece toward the axis of the insulator so as to enable the pin plug to be smoothly inserted into the sleeve etc. of the jack and extracted therefrom, and furthermore, to obtain a good electric contact between the sleeve of the jack and itself by the elasticity of the cover and the contact piece.
It is the third object of the present invention to provide a pin plug which is improved in corrosion resistance and easy coloring so as to be identified by a color code at the sleeve thereof with ease.
It is the fourth object of the present invention to provide a pin plug which can be manufactured more easily by integrally forming the insulator having a cylindrical sleeve portion by rigid resin molding so as to fix the metal contact piece and the center pin therein.
In order to achieve the above objects, the pin plug according to the present invention comprises a cylindrical sleeve to which a first conductor of a cord having the first and a second conductors therein is connected, a center pin disposed along the axis of the sleeve, one end of which projects from the sleeve and the other end of which is connected to the second conductor of the cord, an insulator for electrically insulating the sleeve from the center pin and for fixing them each other, and a non-rigid resin cover which engages the outside of the sleeve.
The sleeve and the insulator set forth above are integrally formed with rigid resin into a two-partitioned component, the sleeve includes an opening at a part of the circumference of the cylindrical sleeve portion thereof, and a flexible metal contact piece connected to the first conductor of the cord is attached to the opening so as to be radially displaceable.
The objects of the present invention set forth above, other objects and new characteristic thereof will be more completely understood by reading the following detailed description with reference to attached drawings. The drawings, however, is exclusively for explanation and does not limit the scope of the present invention thereto.